1. Field of the Invention
This invention involves a new class of compounds, geminal-bis(difluoramino)-substituted heterocyclic nitramines, and the production thereof. More specifically, this invention involves the production of 3,3-bis(difluoramino)octahydro-1,5,7,7-tetranitro-1,5-diazocine (TNFX), which may be formulated into explosives and propellant oxidizers.
2. Description of the Related Art
The synthesis of certain examples of this class of compounds, geminal-bis(difluoramino)-substituted heterocyclic nitramines, is difficult and nonintuitive. The certain examples that are particularly synthetically difficult are molecules that incorporate the geminal-bis(difluor-amino)alkylene [C(NF2)2] component and the nitramine component [Nxe2x80x94NO2] in close proximity, especially when separated by only a methylene (CH2) link in order to maintain a low fuel-to-oxidizer component ratio and concomitantly high oxygen balance in the product molecule. This invention involves 3,3-bis(difluoramino)octahydro-7,7-dinitro-1,5-diazocine derivatives (a heretofore unknown specific class of compound) and novel precursors to these new derivatives, by the use of certain key intermediates and reagents which allow formation of this target structural subcomponent.
The calculated performance improvements expected from geminal-bis(difluoramino)-substituted heterocyclic nitramines when formulated into explosives and propellants has been reported. [Miller, Materials Research Society Proceedings 1996, 418, 3]
Methodology for preparing a geminal-bis(difluoramino)-substituted nitrogenous heterocycle has been reported in Chapman et al. Journal of Organic Chemistry 1998, 63, 1566, incorporated herein by reference, who describe the preparation of 3,3,7,7-tetrakis(difluoramino) octahydro-1,5-bis(4-nitrobenzenesulfonyl)-1,5-diazocine; this intermediate was converted to the corresponding nitramine, 3,3,7,7-tetrakis(difluoramino) octahydro-1,5-dinitro-1,5-diazocine, given the acronym HNFX as discussed in Chapman et al, Journal of Organic Chemistry 1999, 64, 960, incorporated herein by reference.
Methodology for preparing a structurally similar geminal-dinitro-substituted nitrogenous heterocycle has been reported by Cichra and Adolph [Synthesis 1983, 830], who describe the preparation of octahydro-1,3,3,5,7,7-hexanitro-1,5-diazocine.
However, the preparation of asymmetric octahydro-1,5-diazocine derivatives incorporating both geminal-dinitro and geminal-bis(difluoramino) substituents has not been previously described. A particularly attractive target compound in terms of providing this asymmetric functionality would be 3,3-bis(difluoramino)octahydro-1,5,7,7-tetranitro-1,5-diazocine, given by us the acronym TNFX by analogy to the acronyms HNFX and RNFX. The incorporation of both functionalities provides a difluoramino component desired for energetic combustion of metallized-fuel propellant formulations, and the gem-dinitro component provides higher oxygen balance (for more-complete combustion) than analogous all-difluoramino derivatives.
The present invention relates to 3,3-bis(difluoramino)octahydro-1,5,7,7-tetranitro-1,5-diazocine (TNFX) and precursors leading to TNFX and provides a process for the preparation of TNFX having the formula: 
A preferred embodiment of the present invention relates to methods for the preparation of certain new geminal-dinitro-1,5-diazocine derivatives which are suitable precursors leading to TNFX. The invention also involves novel and nonintuitive methods for the preparation of TNFX, a specific member of a general class of compounds with the substructure 3,3-bis(difluoramino)octahydro-7,7-dinitro-1,5-diazocine. TNFX is produced by the use of intermediates which allow formation of the target structural subcomponents, octahydro-3,3-dinitro-1,5-diazocine and a more specific substructure of 3,3-bis(difluoramino)octahydro-7,7-dinitro-1,5-diazocine.
In a preferred embodiment of the present invention, the substitution on heterocyclic precursors"" nitrogen atoms is significant. The nitrogen atoms of heterocyclic precursors (such as diazocines) must be suitably substituted, or xe2x80x9cprotected,xe2x80x9d during the process of difluoramination to allow this process to proceed to geminal-bis(difluoramino)alkylene derivatives. Without suitable protection of proximate multiple nitrogens, especially those separated from reacting carbonyl sites by a short bridge, such as methylene, the process of difluoramination of ketone intermediates does not proceed to geminal-bis(difluoramino)alkylene derivatives. The result is mono(difluoramino) alkylene derivatives or no reaction at all.
In a preferred embodiment of the present invention, the method of making a 3,3-bis(difluoramino)octahydro-1,5,7,7-tetranitro-1,5-diazocine comprises reacting a hexahydro-7,7-dinitro-1,5-bis(nitrobenzenesulfonyl)-1,5-diazocin-3(2H)-one with a difluoramine source to produce a 3,3-bis(difluoramino)octahydro-7,7-dinitro-1,5-bis(nitrobenzenesulfonyl)-1,5-diazocine and reacting said 3,3-bis(difluoramino)octahydro-7,7-dinitro-1,5-bis(nitrobenzenesulfonyl)-1,5-diazocine with a highly reactive nitrating reagent in the presence of a strong Lewis acid, such as antimony pentafluoride, boron triflate or boron fluorosulfonate.
An object of a preferred embodiment of the present invention is to create a novel explosive and propellant oxidizer involving geminal-bis(difluoramino)-substituted heterocyclic nitramines.
Another object of a preferred embodiment of the present invention is to provide a method of producing 3,3-bis(difluoramino)octahydro-1,5,7,7-tetranitro-1,5-diazocine (TNFX).
Yet another objective of object of a preferred embodiment of the present invention is provide a method of producing TFNX in appreciable yield by removing the electron withdrawing nitrobenzene sulfonyl nitrogen protecting groups on 3,3-bis(difluoramino)octahydro-7,7-dinitro-1,5-bis(nitrobenzenesulfonyl)-1,5-diazocine with sufficiently reactive nitrating reagent.